This invention relates to the field of retroreflectors, and more particularly, to a hollow retroreflector assembly mounted on a mounting member.
Hollow retroreflectors are old in the art. Hollow retroreflectors are made of three plates joined together having optically flat reflective surfaces disposed at right angles to each other, and meeting at what can be described as a common inside corner of an imaginary cube. Hollow retroreflectors in general have the essential property of causing incident and reflected light rays to travel along parallel paths.
When hollow retroreflectors are assembled for high accuracy and precision it is always essential to ensure that the reflective surfaces remain mutually perpendicular and sometimes essential to ensure that the retroreflector assembly as a whole does not move.
The perpendicularity of the reflective surfaces is affected by external stresses. Examples of such external stresses are thermal expansion or contraction of the substrate material from which the retroreflector is made, deflection caused by curing of the adhesives which join members of the retroreflector and/or mass. Accordingly, it is desirable to assemble a hollow retroreflector in such a manner as to reduce the stresses, and also to have a mounting assembly which does not add to these stresses and securely retains the retroreflector thereon. Examples of hollow retroreflector mounting assemblies which have proven successful in maintaining the reflective surfaces in their perpendicular orientations are:
U.S. Pat. No. 3,977,765, to Morton S. Lipkins, which discloses a hollow retroreflector mounted to a support structure through means of applying an adhesive into the joints formed between joined members of the retroreflector and a flat surface of the support structure. This method of mounting the hollow retroreflector ensures that the stresses associated with the curing of the adhesive are primarily translated along the reflective surfaces, not in such a manner as to cause deflection of those surfaces; and
U.S. Pat. No. 5,122,901, to Zvi Bleier, which discloses a hollow surveying retroreflector assembly having a hollow retroreflector mounted within a receptacle. The receptacle has a conically configured interior for receiving the retroreflector and for maintaining the perpendicular alignment of the reflective surfaces of the plates of the retroreflector. The receptacle is then received within an outer casing to allow for mounting of the entire assembly.
The present hollow retroreflector assembly with hard mount assembly also achieves secure mounting of the retroreflector without applying stresses which would deflect the reflective surfaces, while also keeping the retroreflector from moving. Specifically, it is often important when measuring distances using a retroreflector to reduce to a minimum any fluctuations (however small) which may occur because of movement of the retroreflector between successive measurements due to the external stresses of mass and/or temperature change. The mounting assembly of the present invention reduces this movement to a minimum.
The mounting assembly also allows for easy and secure mounting of the retroreflector onto a support.